UK to US Ring Size Conversion

UK to US Ring Size Conversion Chart 2026 – Free Calculator

The complete UK to US ring size conversion guide 2026 — instantly convert any UK ring size letter (A–Z+2) to a US ring size number, full UK/US conversion table with MM circumference and diameter, common UK/US size pairs for women and men, how the US sizing system works vs UK, conversion formula, buying from US retailers with a UK size, and a free UK↔US ring size calculator.

🇬🇧→🇺🇸 UK Letter to US Number 🇺🇸→🇬🇧 US Number to UK Letter 📋 Full A–Z+2 Conversion Table 🧮 Free UK↔US Calculator 📏 MM Circumference & Diameter 🛍️ US Online Shopping Guide 👫 Most Common UK/US Pairs 📅 2026 Updated

UK to US Ring Size Conversion – The Key Difference

The UK and US ring sizing systems measure the same physical ring sizes but express them in completely different formats. The UK system uses letters from A to Z+2 — the most commonly worn UK women's size is UK M and the most common men's size is UK T. The US system uses numbers — typically ranging from size 3 to 13 for adults, available in whole, half, and quarter sizes. UK M converts to US 6. UK T converts to US 9.625. The two systems are not proportionally simple — you cannot add or subtract a fixed number to convert between them. Always use the conversion chart below rather than estimating, particularly for important ring purchases.

🇬🇧 UK M = 🇺🇸 US 6 (most common ♀) 🇬🇧 UK T = 🇺🇸 US 9.625 (most common ♂) 🔄 No fixed offset — always use chart 📏 Both based on internal circumference MM 🌍 US sizes also used in Canada

UK M

🇬🇧→🇺🇸 Converts to
US Size 6 (Avg ♀)

US 6

🇺🇸→🇬🇧 Converts to
UK Size M (Avg ♀)

UK T

🇬🇧→🇺🇸 Converts to
US 9.625 (Avg ♂)

US 10

🇺🇸→🇬🇧 Converts to
UK Size U–V (Avg ♂)

🔍 UK vs US Ring Size System – How Each Works

🇬🇧 The UK Ring Size System

🔡Uses letters A through Z+2 — 28 sizes in total, running from the smallest child's size (A = 37.8mm circumference) to the largest bespoke size (Z+2 = 71.0mm circumference).
📏Each UK letter = approximately 1.25–1.3mm circumference increase. The scale is highly consistent throughout the A–Z+2 range.
💍Most common UK women's size: UK M (52.5mm / 16.7mm diam). Most common UK men's size: UK T (61.4mm / 19.5mm diam).
🌍Used in: United Kingdom, Republic of Ireland, Australia, New Zealand, and South Africa. AU/NZ sizes are identical letters to UK sizes.
🏪Standard at all UK jewellers: H.Samuel, Beaverbrooks, Ernest Jones, Goldsmiths, Tiffany UK, and all independent UK jewellers use UK letter sizing exclusively.

🇺🇸 The US Ring Size System

🔢Uses numbers — typically from 3 to 13 for adults, including whole sizes, half sizes (e.g., 6.5), and quarter sizes (e.g., 9.25, 9.625). Also used in Canada.
📏Each US full size = approximately 2.55mm circumference increase. Each US half-size = approximately 1.27mm circumference — similar to one UK letter.
💍Most common US women's size: US 6 (= UK M, 52.5mm circ). Most common US men's size: US 9–10 (= UK T–U, 61–63mm circ).
🌍Used in: United States and Canada. Also used by many international online retailers targeting the US market (Etsy US sellers, Amazon US, US-based jewellery brands).
🛍️When ordering from US retailers: Never enter your UK letter — always convert first using the chart below. US retailers do not recognise UK letter sizing.

⭐ Most Common UK to US Ring Size Pairs – Quick Reference

UK L

↕

US 5½

51.2mm circ · 16.3mm ⌀

Popular ♀

UK M

↕

US 6

52.5mm circ · 16.7mm ⌀

⭐ UK Avg ♀

UK N

↕

US 6½

53.8mm circ · 17.1mm ⌀

Popular ♀

UK O

↕

US 7

55.1mm circ · 17.5mm ⌀

Unisex

UK P

↕

US 7½

56.3mm circ · 17.9mm ⌀

Unisex

UK S

↕

US 9⅛

60.2mm circ · 19.1mm ⌀

Popular ♂

UK T

↕

US 9⅝

61.4mm circ · 19.5mm ⌀

⭐ UK Avg ♂

UK U

↕

US 10¼

62.7mm circ · 20.0mm ⌀

Popular ♂

🧮 Free UK to US Ring Size Converter – 2026 Calculator

Convert UK ring size to US instantly — or convert US ring size to UK. Enter your size or MM measurement for full results.

Conversion Result

—

📋 Complete UK to US Ring Size Conversion Chart – A to Z+2 (2026)

📋 How to Use This UK/US Conversion Table

Find your UK size letter in the first column to read across to the US size number, circumference in MM, and diameter in MM. Or find your US size number in the US column and read across to the UK letter. Rows highlighted in purple are the most commonly ordered sizes. Note that some UK sizes correspond to quarter US sizes (e.g., UK T = US 9.625) — when ordering from a US retailer that only offers whole or half sizes, always round up to the nearest available size for an all-day ring.

🇬🇧 UK Size	🇺🇸 US Size	📏 Circ (MM)	📐 Diam (MM)	🇪🇺 EU	🇯🇵 JP	🇦🇺 AU/NZ	Typical Wearer
A	—	37.8	11.9	38	—	A	Small child
B	—	39.1	12.3	39	—	B	Child/pinky
C	1	40.4	12.7	40	1	C	Child/pinky
D	2	41.7	13.1	42	3	D	XS Women
E	2.5	43.0	13.5	43	5	E	XS Women
F	3	44.2	13.9	44	6	F	Small ♀
G	3.5	45.5	14.3	45	7	G	Small ♀
H	4	46.8	14.7	47	8	H	Small ♀
I	4.25	47.4	15.1	47	9	I	Women
J	4.625	48.7	15.5	49	10	J	Women
K	5.125	50.0	15.9	50	11	K	Women
L ⭐	5.5	51.2	16.3	51	12	L	Popular ♀
M ⭐	6	52.5	16.7	53	13	M	UK/US Avg ♀ ⭐
N ⭐	6.5	53.8	17.1	54	14	N	Popular ♀
O	7	55.1	17.5	55	15	O	Unisex
P	7.5	56.3	17.9	56	16	P	Unisex
Q	8	57.2	18.2	58	17	Q	Slim ♂
R	8.625	58.9	18.6	59	18	R	Men
S	9.125	60.2	19.1	60	19	S	Men
T ⭐	9.625	61.4	19.5	61	20	T	UK/US Avg ♂ ⭐
U ⭐	10.25	62.7	20.0	63	21	U	Popular ♂
V ⭐	10.625	64.0	20.3	64	22	V	Popular ♂
W	11.125	65.3	20.7	65	23	W	Large ♂
X	11.625	66.6	21.1	66	24	X	Large ♂
Y	12	67.8	21.5	68	25	Y	XL ♂
Z	12	68.5	21.8	69	26	Z	XL ♂
Z+1	12.5	69.7	22.2	70	27	Z+1	Custom
Z+2	13	71.0	22.6	72	28	Z+2	Bespoke

🇬🇧 UK M = 🇺🇸 US 6 · most common ♀ in both countries

🇺🇸 US size = UK letter — never enter UK letter on US checkout

⭐ Purple rows = most commonly ordered sizes in UK & US

🇦🇺 AU/NZ = same letters as UK — direct match, no conversion needed

🔢 UK ↔ US Ring Size Conversion Formula

⚠️

There Is No Simple Addition/Subtraction Formula Between UK and US Sizes

Unlike metric/imperial conversions, UK and US ring sizes do not have a fixed offset — you cannot simply add or subtract a constant number to convert between them. UK M ≠ US M (US uses no letters). UK size 6 does not exist. US 6 = UK M, but UK N ≠ US 6+1. Always use the chart above or calculator above for accurate conversions. The approximate formula below is for estimation only — never use it for important ring purchases.

UK → US Approximate Formula (Estimation Only)

US size ≈ (UK circumference in mm − 36.5) ÷ 2.55

Example: UK M = 52.5mm → (52.5 − 36.5) ÷ 2.55 = 16.0 ÷ 2.55 = US 6.27 (actual: US 6 ✅)

Example: UK T = 61.4mm → (61.4 − 36.5) ÷ 2.55 = 24.9 ÷ 2.55 = US 9.76 (actual: US 9.625 — close ✅)

⚠️ Use chart for exact values. Formula is accurate to ±0.25 US size in most cases.

US → UK Approximate Formula (Estimation Only)

UK circumference (mm) ≈ (US size × 2.55) + 36.5 → look up chart

Example: US 6 → (6 × 2.55) + 36.5 = 15.3 + 36.5 = 51.8mm → nearest UK size = UK M (52.5mm ✅)

Example: US 8 → (8 × 2.55) + 36.5 = 20.4 + 36.5 = 56.9mm → nearest UK size = UK P–Q (56.3–57.2mm ✅)

When US Retailer Only Offers Whole/Half Sizes — Rounding Rule

If your exact US conversion is a quarter size, always round UP to the next available half size

Example: UK T = US 9.625 — retailer only offers US 9 or US 10 → order US 10 (round up)

Example: UK I = US 4.25 — retailer only offers US 4 or US 4.5 → order US 4.5 (round up)

Example: UK R = US 8.625 — retailer only offers US 8.5 or US 9 → order US 9 (round up)

✅ Rounding up ensures the ring passes over the knuckle and can be worn all day. A slightly loose ring is always better than a ring that will not go on.

US Half-Size vs UK Letter — How They Compare

1 US half-size ≈ 1.275mm circumference ≈ 1 UK letter

This means UK letters and US half-sizes are approximately equivalent in step size — moving from UK M to UK N is roughly the same physical difference as moving from US 6 to US 6.5.

However, 1 full US size ≈ 2.55mm circumference ≈ 2 UK letters.

Example: UK M (52.5mm) → UK N (53.8mm) = +1.3mm ≈ US 6 → US 6.5 = +1.275mm ✅

🛍️ Buying from US Retailers with a UK Ring Size – Complete Guide

🛍️

Key Rule: Always Convert Before Ordering — Never Enter Your UK Letter on a US Checkout

US retailers (Amazon US, Etsy US sellers, Kay Jewelers, Zales, James Allen, Blue Nile, Brilliant Earth) all use US number sizing. If you enter "UK M" in the size field of a US retailer, it will not be understood and you will likely receive the wrong size or your order will be rejected. Always convert your UK letter to a US number using the chart above before placing any order on a US platform.

🔄 Step 1 — Convert your UK size to US before you start shopping. Look up your UK letter in the conversion chart above and note the US size number. Write it down before you begin browsing — it is easy to forget the converted size mid-purchase and default to entering your UK letter by mistake. For the most commonly ordered sizes: UK L = US 5.5, UK M = US 6, UK N = US 6.5, UK O = US 7, UK T = US 9.625, UK U = US 10.25.
📐 Step 2 — Check whether the US retailer offers quarter sizes, half sizes, or whole sizes only. Premium US jewellers (James Allen, Blue Nile, Tiffany US) typically offer quarter sizes — so you can order the exact conversion (e.g., US 9.625 for UK T). High street US retailers (Kay Jewelers, Zales) and most Amazon and Etsy sellers typically offer whole and half sizes only — in this case, apply the rounding-up rule above. Budget retailers may offer whole sizes only — if so, always round up to the next whole size above your conversion value.
📦 Step 3 — Check the US retailer's returns and resize policy before ordering. Major US online jewellers (James Allen, Blue Nile, Brilliant Earth) offer free lifetime resizing. Amazon US has a 30-day return window for most jewellery. Etsy US sellers have variable policies — always check the individual seller's policy page before ordering. UK Consumer Contracts Regulations give you 14-day return rights for items shipped to a UK address from a US retailer — but this does not override the seller's specific policy. Always check before you buy.
💍 Step 4 — Apply wide band adjustment before ordering if the ring is 6mm or wider. Convert your UK size to US first, then if the ring is a wide wedding band (6mm+), add 0.5 US sizes to the converted value before ordering. Example: UK T wide band = US 9.625 + 0.5 = order US 10. This applies to US and UK rings equally — wide bands always feel tighter at the same nominal size than narrow rings due to increased finger contact surface.
🌍 Etsy-specific tip: Message the seller before ordering to confirm they use US sizing. Most US-based Etsy sellers list in US sizes, but not all. Some Etsy sellers operate globally and list in EU (circumference in mm) or UK letter sizing — particularly sellers based in Germany, France, or the UK. Always message: "Please confirm — do you use US number sizing for this ring?" before placing the order to avoid a conversion error.
💰 Factor in import duty and VAT when ordering from US jewellers. As of 2026, rings imported into the UK from the US with a declared value over £135 are subject to UK import VAT (20%) and potentially customs duty (2.5% for silver jewellery, 2.5% for gold). The US retailer typically declares the full purchase value. Budget for an additional 22.5% on top of the US retail price for high-value rings — this applies even if the US retailer offers "free international shipping."

❓ UK to US Ring Size Conversion – FAQ 2026

What is UK ring size M in US size? ▾

UK ring size M converts to US ring size 6. UK M has an internal circumference of 52.5mm and an internal diameter of 16.7mm. US 6 has the same circumference and diameter — both describe exactly the same physical ring, just expressed in different sizing systems. UK M / US 6 is the most commonly ordered ring size for women in both the UK and United States — it is the statistical average women's ring size in both countries.

What is UK ring size T in US size? ▾

UK ring size T converts to US ring size 9.625. UK T has an internal circumference of 61.4mm and a diameter of 19.5mm. US 9.625 is a quarter size — not all US retailers offer this exact size. If ordering from a US retailer that only offers whole or half sizes, order US 10 (round up to the nearest half size above). UK T is the most commonly ordered ring size for men in the UK, corresponding approximately to the US average men's ring size of US 9–10.

Is there a simple formula to convert UK ring size to US? ▾

There is no simple add-or-subtract formula between UK letters and US numbers — you cannot convert between them without using a chart or formula. The approximate estimation formula is: US size ≈ (UK circumference in mm − 36.5) ÷ 2.55. For example, UK M = 52.5mm → (52.5 − 36.5) ÷ 2.55 ≈ US 6.27 (actual: US 6). However, this formula is for estimation only — always use the full conversion chart above for accurate results when making a ring purchase.

What US ring size is UK N? ▾

UK ring size N converts to US ring size 6.5. UK N has a circumference of 53.8mm and a diameter of 17.1mm. US 6.5 is a half size that is widely available from all major US retailers (Amazon, Etsy, Blue Nile, James Allen, Kay Jewelers, Zales). UK N is one of the most popular women's ring sizes in the UK — the conversion to US 6.5 is clean and straightforward with no rounding required.

What is US ring size 7 in UK? ▾

US ring size 7 converts to UK ring size O. US 7 / UK O has a circumference of 55.1mm and a diameter of 17.5mm. UK O is a unisex size, suitable for women with slightly larger fingers and men with slimmer fingers. The conversion from US 7 to UK O is a clean, exact match — no rounding is required. If you are converting from a US 7 wide band to UK, order UK P (one letter up from UK O) to accommodate the wider band's tighter fit.

Does Amazon UK use UK or US ring sizes? ▾

Amazon UK uses UK letter sizing for rings listed by UK-based sellers and UK-stocked items. However, Amazon's global marketplace means some rings listed on Amazon UK are actually fulfilled by US or European sellers — these may list sizes in US numbers or EU circumference numbers. Always check the size format on the product page before ordering. If the sizes listed are numbers between 3 and 13 (e.g., "Size 6, 6.5, 7"), the seller is using US sizing and you need to convert your UK letter to a US number before ordering.

Are UK and Australian ring sizes the same? ▾

Yes — UK and Australian/New Zealand ring sizes use identical letter sizing (A through Z+2). UK ring size M = AU/NZ ring size M — no conversion is needed. This also applies to South African ring sizing. If you are ordering from an Australian jeweller or retailer, your UK ring size letter is directly usable without any conversion. This is the simplest international sizing relationship — the only one that requires no conversion at all.

What is US ring size 6 in UK mm? ▾

US ring size 6 has an internal circumference of 52.5mm and an internal diameter of 16.7mm — corresponding to UK ring size M. To measure this at home: cut a 5mm paper strip, wrap it around the base of your ring finger, mark and measure the overlap. A reading of 52–53mm means you are a UK M / US 6. Alternatively, place a ring that fits on a ruler and measure 16.7mm internal diameter to confirm US 6 / UK M.

🔗 Related Ring Size Guides & Resources

📚 Related Guides on This Site

💍 Ring Size Guide UK – Master Hub 📐 Ring Size Guide – Diameter & Circumference 🛍️ Ring Size Guide for Online Shopping 🔧 Ring Size Guide for Resizing 📊 Average Ring Size UK 2026 😣 Ring Size Guide for Tight Rings

🇺🇸 US Jeweller Ring Size Tools

💎 Blue Nile – Ring Size Guide US 💍 James Allen – Ring Sizing Guide 🌍 Brilliant Earth – Ring Size Guide 🔵 Tiffany & Co UK – Ring Size Guide

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